Polycythemia vera

Polycythemia vera
Updated: 08/31/2024
© Jun Wang, MD, PhD

General features
  • Clonal neoplastic proliferation of multipotent myeloid stem cells
  • Elevated absolute red blood cell mass because of uncontrolled red blood cell production
  • Usually older population
Clinical presentations
  • Associated with polycythemia and platelet dysfunction
  • Stasis of blood flow and local hypoxia
  • Plethora (redness) and cyanosis (Blue) complexion in the face, palms, etc
  • Hepatosplenomegaly, resulted from extramedullary hematopoiesis
  • Thrombotic and bleeding episodes
  • Iron deficiency associated with bleeding
  • Pruritis or peptic ulcers, due to elevated levels of histamine
  • Hypertension
Clinical course
  • Pre-polycythemic: Slightly increased RBC mass
  • Overt polycythemic: Significantly increased RBC mass
  • ‘Spent' or post-polycythemic: Ineffective hematopoiesis, marrow fibrosis, extramedullary hematopoiesis, and anemia
Key pathogenesis
  • Activating mutation of JAK2
  • JAK2: mediates signaling for various receptors, including erythropoietin (EPOR) and thrombopoietin (THPOR)
Key Laboratory findings
  • Elevated absolute red blood cell mass, RBC count, Hgb
  • Commonly thrombocytosis
  • May have hyperuricemia or gout
Key morphological features
Key features for diagnosis
  • Polycythemia vera
    • Marked increased red cell mass: Hb>18.5 g/dL in men, or >16.5 g/dL in women
    • Hypercellular marrow
    • Presence of JAK2 V617F or JAK2 exon 12 mutation
    • Low serum erythropoietin 
  • Post polycythemic myelofibrosis
Differential diagnosis
  • Secondary polycythemia due to dehydration, smoking, high altitude (increased erythropoietin levels)
  • Chronic myelogenous leukemia: BCR-ABL, NO erythroid hyperplasia, Low LAP
  • Essential thrombocythemia:  Hemoglobin (<16.5 g/dL in men and <16.0 g/dL in women), hematocrit (<49 percent in men and <48 percent in women)
Genetic abnormalities
  • Activating JAK2 mutation

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